Microfibrillated cellulose as rheology modifier in adhesives

Abstract

The present invention relates to starch-based adhesive compositions comprising microfibrillatedcellulose (“MFC”). In addition to microfibrillated cellulose, these adhesive compositions comprise at least one starch and/or at least one starch derivative.

The invention claimed is: 
     
       1. An adhesive composition comprising:
 at least one starch and/or at least one starch derivative, in an amount of 5% w/w to 60% w/w, dry matter, of overall adhesive composition; 
 at least one solvent, in an amount of 30% w/w to 95% w/w of the overall adhesive composition; and 
 microfibrillated cellulose in an amount of 0.001% w/w to 10% w/w, dry matter, of the overall adhesive composition, wherein a diameter of the microfibrillated cellulose is in nanometer range, and wherein the microfibrillated cellulose has a Schopper-Riegler (SR) method value of below 95, as determined according to EN ISO 5267-1 (in the version of 1999), or, in the alternative, cannot be reasonably measured in accordance with the SR method, as fibers of the MFC are so small that a large fraction of the fibers simply pass through a screen as defined in the SR method. 
 
     
     
       2. The composition according to  claim 1 , wherein at least one of (i) the amount of microfibrillated cellulose in said composition is from 0.01% dry matter, relative to overall weight of said composition, to 10%; (ii) the amount of microfibrillated cellulose in said composition is from 0.02% w/w relative to the overall weight of the composition to 8% w/w; and (iii) the amount of microfibrillated cellulose is from 0.003% w/w to 22% w/w, as measured relative to an overall amount of starch in said composition. 
     
     
       3. The composition according to  claim 2 , wherein at least one of (i) the amount of microfibrillated cellulose in said composition is from 0.05% dry matter, relative to the overall weight of the composition, to 2%; (ii) the amount of microfibrillated cellulose in said composition is from 0.05% w/w relative to the overall weight of the composition to 0.5% w/w; and (iii) the amount of microfibrillated cellulose is from 0.2% w/w to 1.4% w/w, as measured relative to the overall amount of starch in said composition. 
     
     
       4. The composition according to  claim 2 , wherein at least one of (i) the amount of microfibrillated cellulose in said composition is from 0.05% dry matter, relative to the overall weight of the composition, to 0.15%; (ii) the amount of microfibrillated cellulose in said composition is from 0.05% w/w relative to the overall weight of the composition to 0.5% w/w; and (iii) the amount of microfibrillated cellulose is from 0.2% w/w to 0.6% w/w, as measured relative to the overall amount of starch in said composition. 
     
     
       5. The composition according to  claim 1 , wherein an overall amount of starch in said composition is from 15% w/w to 50% w/w of the overall adhesive composition. 
     
     
       6. The composition according to  claim 1 , wherein the pH value of the adhesive composition is from 8 to 14. 
     
     
       7. The composition according to  claim 1 , wherein the at least one starch is a native starch, or a chemically or physically modified starch, or a starch derivative, or a mixture thereof. 
     
     
       8. The composition according to  claim 1 , wherein the microfibrillated cellulose is characterized in that it results in gel-like dispersion that has a zero shear viscosity, go, of at least 2000 Pas, as measured in polyethylene glycol (PEG), and at a solids content of the microfibrillated cellulose of 0.65%. 
     
     
       9. The composition according to  claim 1 , wherein the microfibrillated cellulose is characterized by a water holding capacity of more than 30, as measured by diluting MFC samples to a 0.3% solids content in water, and then centrifuging the samples at 1000 G for 15 minutes, after which a clear water phase is separated from sediment and the sediment is weighed, wherein the water holding capacity is given as (mV/mT) −1  wherein mV is the weight of the sediment when wet and mT is the weight of dry MFC analyzed. 
     
     
       10. The composition according to  claim 1 , wherein the microfibrillated cellulose is a non-modified (native) microfibrillated cellulose. 
     
     
       11. A method comprising:
 providing an adhesive composition according to  claim 1 ; and 
 manufacturing a corrugated paperboard/cardboard using the adhesive composition. 
 
     
     
       12. A process for making corrugated paperboards or cardboards, said process comprising at least the following steps:
 providing a starch-based adhesive composition according to  claim 1 ; 
 applying said starch-based adhesive composition to at least a part of tips of flutes of a corrugated pieces of paper, on at least one side; and 
 in a corrugator, applying at least one liner onto said corrugated piece of paper, and 
 preparing a single, double, triple or further multiple wall cardboard. 
 
     
     
       13. A corrugated paperboard or cardboard having at least one flute and at least one liner and comprising an adhesive composition according to  claim 1 . 
     
     
       14. The composition according to  claim 1 , wherein the microfibrillated cellulose is a non-modified microfibrillated cellulose derived from plant material. 
     
     
       15. A process for preparing a starch-based adhesive, or an adhesive based on a starch derivative, the process comprising the steps of:
 (a) mixing at least one starch and/or at least one starch derivative, or a mixture thereof, with at least one solvent comprising water; 
 (b) during or after step (a): adding microfibrillated cellulose; and 
 (c) dispersing the mixture of (b) until a homogenous mixture is obtained, 
 
       wherein a diameter of the microfibrillated cellulose is in nanometer range, and wherein the microfibrillated cellulose has a Schopper-Riegler (SR) method value of below 95, as determined according to EN ISO 5267-1 in the version of 1999), or, in the alternative, cannot be reasonably measured in accordance with the SR method, as fibers of the MFC are so small that a large fraction of the fibers simply pass through a screen as defined in the SR method. 
     
     
       16. The process according to  claim 15 , wherein a viscosity of the mixture increases by at least 10% in step (b) and relative to viscosity of the mixture of step (a). 
     
     
       17. The process according to  claim 15 , wherein in step (a), first a primary starch is added to a solvent, then in or after step (a), a secondary starch is added, wherein the secondary starch is the same or a different starch or starch derivative as the primary starch. 
     
     
       18. The process of  claim 15 , wherein the starch-based adhesive or adhesive based on a starch derivative is a composition and at least one of (i) the amount of microfibrillated cellulose in said composition is from 0.001% dry matter, relative to overall weight of said composition, to 10%; (ii) the amount of microfibrillated cellulose in said composition is from 0.02% w/w relative to the overall weight of the composition to 8% w/w; and (iii) the amount of microfibrillated cellulose is from 0.003% w/w to 22% w/w, as measured relative to an overall amount of starch in said composition. 
     
     
       19. The process of  claim 15 , wherein step (a) and/or step (b) comprises adding alkaline in a ratio of dry alkaline relative to dry starch of from 0.1% w/w to 3% w/w. 
     
     
       20. A method comprising using microfibrillated cellulose as a rheology modifying agent in an adhesive comprising a starch and/or starch derivatives, wherein a diameter of the microfibrillated cellulose is in nanometer range, and wherein the microfibrillated cellulose has a Schopper-Riegler (SR) method value of below 95, as determined according to EN ISO 5267-1 (in the version of 1999), or, in the alternative, cannot be reasonably measured in accordance with the SR method, as fibers of the MFC are so small that a large fraction of the fibers simply pass through a screen as defined in the SR method.